The Origins course tracks the origin of all things – from the Big Bang to the origin of the Solar System and the Earth. The course follows the evolution of life on our planet through deep geological time to present life forms.

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DH

A well paced course which helpfully breaks down the different stages highlighting characteristics and progression of both geological and biological periods in Earth's history.

KK

Oct 16, 2016

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What a detailed course with very good examples and knowledgable presenters. I was highly impressed and learned a lot. Very wide in breath of topics. Highly recommended.

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Origins and Early Development of Plants / The Origin and Diversification of Flowering Plants

In module 7, we will have a closer look at the biggest source of oxygen – the plants. Up till now we have heard a lot about the evolution of higher life forms in the oceans. While evolution took a giant step forward in the oceans, the continents remained totally barren for another approx. 100 million years. Vivi Vajda from the Lund University in Sweden and Gitte Petersen will tell you how the plants began to inhabit the terrestrial environment, thus paving the way for other life forms living on land. Land plants have managed to adapt to a very different environment, with new challenges and possibilities. Some of the early plants have survived as fossils – whereas others are still alive. Some of these living fossils will be presented in the videos. We will also have a close look at the biggest group of plants – which has evolved in close collaboration with insects, birds and even some mammals – the flowering plants.

Svend Stouge

Danny Eibye Jacobsen

Jan Audun Rasmussen

Emily Catherine Pope

Transcrição

The ferns enter the stage during the late Devonian, and they have been a very successful plant group ever since. Ferns are vascular plants and reproduce with spores, just as the club mosses but they made revolution in that they developed large lobed leaves that were more and more efficient to capture the sunlight, and at the same time generated new strategies for understorey ecosystems. Ferns soon diversified into a large variety of forms with small plants up to these tree fern types with trunks. Here we have a staghorn fern that has an epiphytic growth habit, meaning that it grows on other plants, often on tree trunks. The spores are generally hidden underneath the leaves. The ferns had their peak during the Mesozoic, but they have remained very successful, and even today, they represent the second-most diverse group of plants specializing in damp understorey and epiphytic niches. Another major revolution in life on land was the appearance of seed bearing plants during the late Devonian. The seed was a structure where by the egg cell, and indeed the whole gametophyte stage of the plant life cycle, was enclosed in the protective tissue of the parent plant. This was a tremendous advantage because it meant that the egg cell received both physical protection and a steady supply of nutrients from the robust parent plant. Although not strictly identical, a seed is somewhat comparable to an egg in the animal world. Both the egg and the seed are advanced life support systems for the new generation. Here we are going to focus on the so-called living fossils, plants that are common during the Mesozoic, but they barely managed to survive a series of mass extinction events and competition from more successful groups to persist in small numbers into the modern age. One characteristic of these living fossils, is that they typically have a very limited diversity, and are restricted to very narrow geographical ranges. One peculiar plant group, that today is completely extinct, are those with fern-like leaves but, they reproduced with seeds instead of spores. These plants got a confusing title "seed ferns". They are afterall not ferns at all. When found in the fossil record it can sometimes be rather difficult to distinguish between the leaves of true ferns and the seed ferns. One must find the distinctive reproductive structures to securely tell them apart. Cycads are seed plants with a woody, usually barrel-shaped trunk, and with a crown of large, stiff, evergreen leaves. They can grow to the size of quite large trees but most are rather small shrub-sized forms. They typically grow very slowly and live for a very long time. A few examples are known that have reached the incredible age of thousand years. Cycads were very common and diverse during the Jurassic, and today they are still three families surviving. They have actually changed remarkably little since the Jurassic, but they occupy much less ecospace than in former times, probably because they have been largely out-competed by the more, opportunistic flowering plants. Here you can see the male cones that produce pollen grains and if we instead look at this female tree, there is a female cone which is more robust and contains ovules instead of pollen. If you look closer at the leaves, you can see that some of them have nasty spines. This is the plant's way to defend itself against herbivores and during the Jurassic this might have been a defense against herbivorous dinosaurs. The Ginkgo tree, as the ones that you see behind me, is another example of living fossils. During the Jurassic, they had a broad geographical distribution spanning all continents and they were represented by many species. But today they survive in the natural state only in a small part of Southwestern China, although they are planted in parks and botanical gardens worldwide just as you can see here as it's a nice ornamental tree. Ginkos are large trees, normally reaching a height of about 35 meters and the leaves are very characteristic. They have a fan-like shape and numerous parallel veins without cross connections. Just as with the cycads, ginkgo trees have separate sexes, some trees are males and other females. Male plants produce small pollen cones, whereas the female plants, have ovules that develop into seeds if they become fertilized. Ginkgos are deciduous which means that they shed their leaves in the autumn. And Ginkgos are also long-lived with some species claimed to be as much as 2,500 years old. Interestingly, they are very resistant to diseases as they contain poisonous agents.